Terahertz time-domain spectroscopy of complex organic molecules in astrophysically-relevant ices

Abstract

With the recent detection of glycine in cometary samples returned by the STARDUST mission (Elsila et al. 2009), the quest to understand the origins of life-essential species like glycine has only increased in intensity. One route to the synthesis of these species is through the reactions of simple mols. in the icy mantles of dust and comets to form larger, more complex org. species. These products can then react to form glycine and other amino acids. While many complex org. species have been detected in the interstellar medium in the gas-phase, detection in the condensed phase in ices is significantly more challenging, largely due to the frequently ambiguous nature of the traditionally-obsd. IR transitions. We have constructed a sensitive setup to study the spectra of complex org. mols. (COMs) embedded in astrophys.-relevant ice analogs using THz time domain spectroscopy. In the THz region of the spectrum covered by our spectrometer (∼300 GHz - 7 THz), we are sensitive to the internal torsional motion displayed by a wide variety of COMs. Here, we present our initial efforts to det. whether or not, and under what conditions, such internal motion is manifest in the THz spectra of these COM-doped ices. We will present preliminary spectra of methanol (CH_3-OH) and Me formate (CH_3COOH) embedded in both pure water ices, as well as more complex mixts. We discuss our results in the context of astronomical observations and the possibility of probing of ice compns. in the absence of a background star.